The image in question is licensed under CC BY 2.0, which requires in section 4(b) [emphasis mine]:
You must keep intact all copyright notices for the Work and give the Original Author credit reasonable to the medium or means You are utilizing by conveying the name (or pseudonym if applicable) of the Original Author if supplied; the title of the Work if supplied; to the extent reasonably practicable, the Uniform Resource Identifier, if any, that Licensor specifies to be associated with the Work, unless such URI does not refer to the copyright notice or licensing information for the Work
The licensor has certainly specified a URL to be associated with the work, and it is certainly practicable to include it. However, insofar as the URL "does not refer to the copyright notice or licensing information for the Work," it appears the CC BY 2.0 license requirements excuse you from including the URL within the required attribution statement.
Even if the URL is required, making it a clickable link is probably not enforceable under the license, though perhaps there's an outside chance a court may view linking, when possible, to be necessary to remain "reasonable to the medium" of the Web. Even in such a case, you may use a nofollow directive in order to thwart any SEO advantage to the author's URL.
Some concerns I have about actually carrying out such an omission in practice:
The author does not explicitly say they should be attributed by name. It is possible they may argue the URL in question is their pseudonym and is meant to be used in place of their name. (A previous U.S. case determined that "CC BY-SA 3.0" legally qualified as a "license URI" to identify the license in use, so stranger things have happened.)
The copyright holder definitely did state a requirement to link to that URL when reproducing his copyrighted work. The question of how that requirement interacts with the statements in the CC BY 2.0 license document is uncertain and may vary by jurisdiction. There is the legal principle of four corners that limits contract obligations to only those expressed in the contract document, but it is unclear to me how this applies to CC BY, a copyright license.
